<meta charset="utf-8">
(#) Using `mm` or `in` dimensions

!!! WARNING: Using `mm` or `in` dimensions
   This is a warning.

Id
:   `InOrMmUsage`
Summary
:   Using `mm` or `in` dimensions
Severity
:   Warning
Category
:   Correctness
Platform
:   Android
Vendor
:   Android Open Source Project
Feedback
:   https://issuetracker.google.com/issues/new?component=192708
Since
:   Initial
Affects
:   Resource files
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/PxUsageDetector.java)
Tests
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/PxUsageDetectorTest.java)
Copyright Year
:   2011

Avoid using `mm` (millimeters) or `in` (inches) as the unit for
dimensions.

While it should work in principle, unfortunately many devices do not
report the correct true physical density, which means that the dimension
calculations won't work correctly. You are better off using `dp` (and
for font sizes, `sp`).

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
res/layout/now_playing_after.xml:49:Warning: Avoid using "mm" as units
(it does not work accurately on all devices); use "dp" instead
[InOrMmUsage]
    android:layout_width="100mm"
    ----------------------------
res/layout/now_playing_after.xml:50:Warning: Avoid using "in" as units
(it does not work accurately on all devices); use "dp" instead
[InOrMmUsage]
    android:layout_height="120in"
    -----------------------------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`res/layout/now_playing_after.xml`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers
&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/now_playing"
    android:layout_width="fill_parent"
    android:layout_height="@dimen/now_playing_height"
    android:orientation="horizontal"&gt;
    &lt;LinearLayout
        android:background="@color/background2"
        android:paddingLeft="14dip"
        android:paddingRight="14dip"
        android:paddingTop="10dip"
        android:paddingBottom="10dip"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_weight="1"
        android:orientation="vertical"&gt;
        &lt;TextView
            android:id="@+id/now_playing_title"
            android:duplicateParentState="true"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:textStyle="bold"
            android:textSize="@dimen/text_size_large"
            android:textColor="@color/foreground1"
            android:text="@string/now_playing_after_title"
            android:maxLines="2"
            android:ellipsize="end" /&gt;
        &lt;TextView
            android:id="@+id/now_playing_subtitle"
            android:duplicateParentState="true"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:paddingTop="3dip"
            android:textColor="@color/foreground2"
            android:textSize="@dimen/text_size_small"
            android:text="@string/now_playing_after_subtitle"
            android:singleLine="true"
            android:ellipsize="end" /&gt;
    &lt;/LinearLayout&gt;
    &lt;View
        android:layout_width="2px"
        android:layout_height="fill_parent"
        android:background="@android:color/white" /&gt;
    &lt;ImageButton
        android:background="@drawable/btn_now_playing_more"
        android:id="@+id/now_playing_more"
        android:src="@drawable/ic_now_playing_logo"
        android:padding="12dip"
        android:layout_width="100mm"
        android:layout_height="120in"
        android:onClick="onNowPlayingLogoClick"
        android:maxHeight="1px"
        android:scaleType="center" /&gt;
&lt;/LinearLayout&gt;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/PxUsageDetectorTest.java)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `PxUsageDetector.testPxWarnings`.
To report a problem with this extracted sample, visit
https://issuetracker.google.com/issues/new?component=192708.

(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Adding the suppression attribute `tools:ignore="InOrMmUsage"` on the
  problematic XML element (or one of its enclosing elements). You may
  also need to add the following namespace declaration on the root
  element in the XML file if it's not already there:
  `xmlns:tools="http://schemas.android.com/tools"`.

  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;resources xmlns:tools="http://schemas.android.com/tools"&gt;
      ...
      &lt;style tools:ignore="InOrMmUsage" .../&gt;
    ...
  &lt;/resources&gt;
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="InOrMmUsage" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'InOrMmUsage'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore InOrMmUsage ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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